Asymptotes

An asymptote is a straight line that constantly approaches a given curve but does not meet at any infinite distance. In other words, Asymptote is a line that a curve approaches as it moves towards infinity.

The curves visit these asymptotes but never overtake them. The method opted to find the horizontal asymptote changes based on how the degrees of the polynomials in the numerator and denominator of the function are compared. If both the polynomials have the same degree, divide the coefficients of the largest degree terms.

Asymptotes Meaning

An asymptote of the curve y = f(x) or in the implicit form: f(x,y) = 0 is a straight line such that the distance between the curve and the straight line lends to zero when the points on the curve approach infinity.

There are three types of asymptotes namely:

  • Vertical Asymptotes
  • Horizontal Asymptotes
  • Oblique Asymptotes

The point to note is that the distance between the curve and the asymptote tends to be zero as it moves to infinity or -infinity.

Horizontal Asymptote

When x moves to infinity or -infinity, the curve approaches some constant value b, and called as Horizontal Asymptote.

Vertical Asymptote

When x approaches some constant value c from left or right, the curve moves towards infinity, or -infinity and this is called Vertical Asymptote.

Oblique Asymptote

When x moves towards infinity or -infinity, the curve moves towards a line y = mx + b, called Oblique Asymptote.

Please note that m is not zero since that is a Horizontal Asymptote.

How to find horizontal asymptotes

To recall that an asymptote is a line that the graph of a function visits but never touches. In the following example, a Rational function consists of asymptotes.

In the above example, we have a vertical asymptote at x = 3 and a horizontal asymptote at y = 1. The curves approach these asymptotes but never visits them.

The method to identify the horizontal asymptote changes based on how the degrees of the polynomial in the function’s numerator and denominator are compared. Below are the points to remember to find the horizontal asymptotes:

  • If the degree of the polynomials both in numerator and denominator is equal, then divide the coefficients of highest degree terms to get the horizontal asymptotes.
  • If the degree of numerator is less than the degree of denominator, then the horizontal asymptotes will be y = 0.
  • If the degree of numerator is greater than the degree of denominator, then there is no horizontal asymptotes.

Examples

1. Find the horizontal asymptotes for f(x) = x+1/2x.

Solution: Given, f(x) = (x+1)/2x

Since, the highest degree here in both numerator and denominator is 1, therefore, we will consider here the coefficient of x.

Hence, horizontal asymptote is located at y = 1/2

2. Find the horizontal asymptotes for f(x) = x/x2+3
Solution: Given, f(x) = x/x2+3

Since, we can see here the degree of numerator is less than denominator, therefore, horizontal asymptote is located at y = 0.

3. Find the horizontal asymptotes for f(x) =(x2+3)/x+1

Solution: Given, f(x) =(x2+3)/x+1

As you can see, the degree of numerator is greater than that of denominator. Hence, there is no horizontal asymptote.